Well pump (Goulds) question

I've got a 4" submersible pump installed and I'm trying to find the specs for it so that I can purchase a new pressure tank.
It's a Goulds and the model number is 5ES03412. It was installed 12 years ago.
Can anyone tell me the discharge rate or the horsepower of this guy?
Thanks.
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specs
years
That should be a 1/3hp due to the 03 but I don't know for sure. If it were a 05 it would be a 1/2 hp (you didn't mis read it or type it incorrectly?), a 5ES10412 (3 wire, control box in the house) is a 1 hp, 15 a 1.5 hp, 07 a 3/4 hp etc.. It's an old model and not produced today but...
You don't size a pressure tank based on the hp of a pump. The hp only relates to the motor, and the motor turns the wet end, or the actual pump if you will. The 5ES says you have a 5 gpm wet end, or pump that uses a 1/3hp motor. Now that, the hp, is then shall we say, regulated by the water level in the well, the depth of the pump, the pressure range you operate the pump at, the TDH (total dynamic head) of the entire water system on and on.
So.... turn on your water at a faucet until the pump turns on, note the pressure, then shut off the water and note the pressure the pump shuts off at; I.E. 30/50. Then take a 5 gallon bucket and run water in it from the drain on your pressure tank tee and time the pump run time and measure how much water you get in 60 seconds. Maybe 2 or more 5 gal buckets will be needed if you have a large pressure tank. You want the pump to run at least 60 seconds (for proper cooling of the motor). The gpm your 'system' delivers to the pressure tank in a minute is the gpm of the system, regardless of what hp and gpm pump you have. Size the tank, based on the drawdown at the pressure range you use, to provide the manufacturers' minimum run time of one minute (60 seconds). This drawdown is the amount of water between the pump shutting off and coming on again. Another drawdown is how far the water level in the well falls when you pump the well for say 15-30 minutes, and you don't need t oknow that for this project.
Caution, many GUYS mistakenly think larger is better, and that's not true in this case or many others. Going to a very large pressure tank (say 40 gallon or more drawdown at 30/50 psi) can cause a dry well condition (pump sucks air), ruin the pump (overheat it), cause poor water quality problems (open other areas of recovery water with high whatever that you don't want in the water; like mud, iron etc.) and possibly, the collapse of some wells.
Gary Quality Water Associates
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wrote

Gary, great post - thanks!
Would it be possible to calculate the desired drawdown by using this formula?
(new drawdown) = (existing tank drawdown) * 60 / (# seconds to complete current cycle)
Essentially I'd like to 'cheat' and calculate the desired tank drawdown capacity, by just assuming pump runtime would scale linearly with tank drawdown capacity. Could it be this easy if we felt like playing with numbers instead?
- Chris
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Yes fewer motor starts equates to longer life but... see my reply to him and the part about the problems with going too large.
Gary Quality Water Associates
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